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Development and Application of a Computer Model for Large-Scale Flame Acceleration Experiments (NUREG/CR-4855)

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Abstract

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NUREG/CR-4855 (PDF - 3.16 MB)

Publication Information

K. D.Marx

July 1987

Sandia National Laboratories Livermore, CA 94550

Operated by Sandia Corporation

for the
U. S. Department of Energy

Prepared for
Division of Reactor Accident Analysis
Office of Nuclear Regulatory Research
U. S. Nuclear Regulatory Commission
Washington, DC 20555

Under Memorandum of Understanding DOE 40-550-75 NRC FIN No. M1246

Availability Notice

Abstract

A new computational model for large-scale premixed flames is developed and applied to the simulation. of flame acceleration experiments. The primary objective is to circumvent the necessity for resolving turbulent flame fronts; this is imperative because of the relatively coarse computational grids which must be used in engineering calculations. The essence of the model is to artificially thicken the flame by increasing the appropriate diffusivities and decreasing the combustion rate, but to do this in such a way that the burn velocity varies with pressure, temperature, and turbulence intensity according to prespecified phenomenological characteristics. The model is particularly aimed at implementation in computer codes which simulate compressible flows. To this end, it is applied to the two-dimensional simulation of hydrog .en-air flame acceleration experiments in which the flame speeds and gas flow velocities attain or exceed the speed of sound in the gas. It is shown that many of the features of the flame trajectories and pressure histories in the experiments are simulated quite well by the model. Using the comparison of experimental and computational results as a guide, some insight is developed into the processes which occur in such experiments.